#include<stdio.h>
int main(){

    int lower, upper, sum = 0;
    scanf("%d %d", &lower, &upper);
    if(lower < 0 || upper < 0 || lower > upper)
    {
        printf("Invalid input");
        return 0;
    }
    for(int i = lower; i <= upper;i++)
    if(i%7 == 0)
        sum += i;
    }
}

     
         printf("%d", sum);

return 0;
}